Analysis and improved performance of RPR protection

Resilient Packet Ring (RPR, IEEE 802.17) is designed with a protection mechanism aiming at restoring traffic on the ring within 50 ms in case of a link or station failure. In this article, we evaluate RPR protection with respect to service disruption, packet reordering and packet loss. Different error scenarios are simulated, with both steering and wrapping protection. Unfortunately, the 50 ms restoration time guarantee can not always be met if in order delivery of packets is required, since RPR uses a quite long (default 40 ms) topology stabilisation period to avoid packet reordering. We suggest a novel protection mechanism, that does not have to wait for the new topology to be stable, and that gives sub 50 ms restoration for all traffic. We also show that for in order delivery of packets, our new mechanisms discards a very low number of packets compared to the mechanism of the RPR standard.